The invention relates to a dental handpiece with a workhead, in which rotation of an element to which compressed air can be applied is converted into vibration of an elastically housed reception part for a dental tool. The plane of vibration of the reception part lies essentially perpendicular to the longitudinal axis of the reception part.
Such a handpiece is known from FIG. 6 of AT 404 550 B. Incoming compressed air acts on an unbalanced turbine rotor which is housed rotatably on the reception part of the tool so that rotating unbalance generates the desired vibrations of the tool (file, brush, polishing tool, etc). Rotary shafts achieve up to 300,000 revolutions per minute and very high stresses inevitably occur in the roller bearings thereof.
The object of the invention is to create a dental handpiece of the type mentioned above, in which no roller bearings are necessary.
This is achieved according to the invention by having a vibration-generating element be formed by a sleeve allocated to the reception part with radial play, towards which sleeve angled outlet nozzles for compressed air are directed. The compressed air which strikes the wall of the sleeve at an angle effects a circular rolling movement of the sleeve, and thus generates the rotating unbalance which brings the reception part and the tool clamped in the reception part to natural oscillations.
In a first version, the angled outlet nozzles are provided inside the sleeve in the reception part. The compressed air is supplied to the outlet nozzles from an axially-distanced inlet chamber via an annular channel extending axially in the reception part, or via several axis-parallel channels.
In a further version, the angled outlet nozzles are provided outside the sleeve in an annular element connected to the reception part which surrounds the sleeve with radial play. As the annular element is connected to the reception part, the radial play between the sleeve and the annular element can be smaller than the radial play between the sleeve and the reception part itself, so that the sleeve circles against the internal wall of the annular element and the vibrations are transferred to the reception part via the annular element. The compressed air is supplied in this version via an annular channel which runs between the annular element and an external sleeve.
To act on the vibration-generating sleeve from the outside, the outlet nozzles can also, for example, be provided at an annular element arranged in the housing of the workhead.
For an elastic bearing of the reception part, a first elastic element in the front area of the reception part and a second elastic element in the rear area are preferably provided. The second elastic element preferably seals off the inlet chamber for the compressed air from the exit chamber. The sleeve is preferably arranged behind the second elastic element at the end of the reception part.
The invention is described in more detail in the following by means of the figures of the accompanying drawings without being limited to them.